Newtons rings on viewfinder bar?

[freshwater_life]

My new M8 has just developed an interesting problem. There are what appear to be "Newton's Rings" on the top bar of my 90mm viewfinder markers.

I cleaned all the windows on the front of the camera just in case these coloured bars/rings were being caused by an oily deposit. This had no effect and the the "rings" are still there. The effect is similar to that observed when delamination occurs in microscope eyepieces.

I checked the other viewfinder settings but the problem is only on the 90mm upper bar.

Has anyone seen this effect before?

Derek

[marknorton]

All three of my M8's do it to a greater or lesser extent, depends where I place my eye.

[gravastar]

Exactly the same experience as Mark with the two I have, one working the other as backup. I've had a camera replaced 3 times by Leica and I noticed that some showed the curved artifacts more than others. I think it's most noticeable at the top of the 90mm frame lines.

Bob.

[cocker]

Isaac would be horrified at what is alleged in his name these days!

[freshwater_life]

Here is a photograph of the artifact that appears in the 90mm upper viewfinder bar. Is this a fault or is it common to all M8s?

Derek

[wstotler]

Originally Posted by freshwater_life

Here is a photograph of the artifact that appears in the 90mm upper viewfinder bar. Is this a fault or is it common to all M8s? Derek

Holy cow. Can't answer your "common" question but my top M8 (or M6TTL) framelines don't have a distortion like this--looks like a fault to me. Thanks, Will

[Paul Hart]

My M8 has this on the top 90 frameline, but a slight downwards adjustment of the eye relative to the finder and it goes.

Hadn't noticed it before this post. Can't imagine it's a fault, or that it matters.

[adan]

You are seeing a part of the rangefinder optical system through the slit - in a piece of metal - that is the frameline.

In the diagram below, you can see the "framelines" are actually slits in a black mask (A) which is illuminated by the serrated frosted glass window on the front of the camera.

Over to the right (B) is a round lens that is part of the optics that direct the secondary RF image across the camera and into the viewfinder.

You are just seeing the top curved edge of that optical group showing through the frameline. Completely normal in a Leica M6 or later (the RF/VF optics changed slightly in the mid-80's)

(Sometimes it is even possible to see a bit of the secondary RF image through the 90 framelines - moving back and forth as you focus).

------------

Would it be out of line to suggest that - before calling something a "fault" - one gains a little knowledge about the actual inner workings of a device?

[freshwater_life]

Originally Posted by adan

You are seeing a part of the rangefinder optical system through the slit - in a piece of metal - that is the frameline.

In the diagram below, you can see the "framelines" are actually slits in a black mask (A) which is illuminated by the serrated frosted glass window on the front of the camera.

Over to the right (B) is a round lens that is part of the optics that direct the secondary RF image across the camera and into the viewfinder.

You are just seeing the top curved edge of that optical group showing through the frameline. Completely normal in a Leica M6 or later (the RF/VF optics changed slightly in the mid-80's)

(Sometimes it is even possible to see a bit of the secondary RF image through the 90 framelines - moving back and forth as you focus).

------------

Would it be out of line to suggest that - before calling something a "fault" - one gains a little knowledge about the actual inner workings of a device?

Many thanks for the information about the artifact in response to my question as to whether this was a fault or a normal occurrence.

Your explanation, along with the diagram was superb.

I only wish that my initial equiry to Leica had produced such a quick and positive response. It would have saved me a lot of unnecessary angst!

I am sorry that my ignorance was showing in my post and would be most grateful if you could give me a reference or pointer to information about the inner workings of the M8.

Derek

[jaapv]

http://www.l-camera-forum.com/leica-...-leica-m8.html

And on things Leica M in general:

Günther Osterloh:
Leica M Hohe Schule der Fotographie (also available in English translation)

Johnathan Eastland:

Leica M compendium

[Speenth]

Originally Posted by adan

You are seeing a part of the rangefinder optical system through the slit - in a piece of metal - that is the frameline.

In the diagram below, you can see the "framelines" are actually slits in a black mask (A) which is illuminated by the serrated frosted glass window on the front of the camera.

Over to the right (B) is a round lens that is part of the optics that direct the secondary RF image across the camera and into the viewfinder.

You are just seeing the top curved edge of that optical group showing through the frameline. Completely normal in a Leica M6 or later (the RF/VF optics changed slightly in the mid-80's)

(Sometimes it is even possible to see a bit of the secondary RF image through the 90 framelines - moving back and forth as you focus).

Recently Ken Tanaka asked the members if they'd ever really learned anything from this forum. I just have. Many thanks for a very informative post.

I'd like to see more of these technical explanations of my beloved M8 (and its lenses etc).

Steve'

[adan]

Derek: actually my "suggestion" wasn't directed at you - nothing wrong with asking the question at all!

A bit more detail (off the original question) for those who expressed interest:

The mask "A" is actually TWO masks, sandwiched close together.

One has slits for all 6 lenses that have internal framing (24/28/35/50/75/90 in the M8; 28/35/50/75/90/135 in a .72x film viewfinder). The other has similar slits but slightly offset from each other. This second mask SLIDES diagonally when lenses are mounted, or when the frame selector lever beside the lens is moved, so that different pairs of slits line up to adjust the framing to the lens mounted.

Slide the second mask one way, and the 28/90 lines in the first mask are revealed, but the others are blocked. Slide it the other way and only the 50/75 lines are uncovered. Leave it in "neutral" (or with no lens mounted) and the 24/35 lines are visible, but not the others.

The whole mask sandwich is linked to the focusing system, and moves down/right or up/left as a unit to compensate for parallax. In theory, some believe, this mask set could be replaced by a transparent LCD with virtual "slits" created electronically, which would allow them to change in size as well as position to make framing equally accurate at both close and long distances. I have my doubts about whether it would be practical, although I'm sure it is possible.

The optical group "B" is what moves side to side to shift the light coming from the RF window at the extreme right, and move the RF patch in the viewfinder. It is linked to the roller/feeler inside the top of the camera's lens mount by a system of bell cranks and levers. As the lens moves in and out to focus, the back of the lens, or a cam in the lens, pushes the roller in and out, and the linkage swings this lens left and right.

The white plate with a hole in it between "A" and "B" is mirror-surfaced on the left side, to bounce the maximum amount of light from the serrated window through the frameline mask.

One last note - the main viewfinder is made up of two wedges of glass, with a semi-reflective surface on the diagonal where they join (far left) that overlays the lines and the RF image on the overall view through the finder.

This solid block of glass reaches almost the full depth of the viewfinder, front to back. Which is why I am highly skeptical when some have suggested a "zooming" viewfinder for the Leica Ms. There is little empty space in which to "zoom" bits of glass back and forth to achieve this.

And in addition, there would also need to be a perfectly matched zooming system somewhere in the chain through "A" and "B" to enlarge or shrink the rangefinder image in perfect sync with the main viewfinder - and I do not see a lot of excess space there for a zooming optical system, either.